Chemical mechanical polishing slurry

ABSTRACT

A chemical mechanical polishing slurry includes liquid and abrasive solid components, with at least some of the abrasive solid component comprising individually non-homogeneous abrasive particles. In one implementation, the non-homogeneous abrasive particles comprise an innermost portion and an outermost portion, with the innermost and outermost portions comprising different materials. In one implementation, the material of the outermost portion is harder than the material of the innermost portion. In one implementation, the material of the outermost portion comprises TiN and the material of the innermost portion comprises SiO 2 . In one implementation, the material of the outermost portion comprises WN and the material of the innermost portion comprises TiN. In one implementation, the material of the outermost portion is softer than the material of the innermost portion.

RELATED PATENT DATA

This patent resulted from a divisional application of U.S. patentapplication Ser. No. 09/717,477, filed Nov. 20, 2000, entitled “ChemicalMechanical Polishing Process”, naming Trung Tri Doan as inventor, thedisclosure of which is incorporated by reference; which resulted from adivisional application of U.S. patent application Ser. No. 09/389,536,filed Sep. 2, 1999, entitled “Laser Pyrolysis Particle Forming Methodand Particle Forming Method”, naming Trung Tri Doan as inventor, nowU.S. Pat. No. 6,254,928 B1, the disclosure of which is incorporated byreference.

TECHNICAL FIELD

This invention relates to particle forming methods, laser pyrolysisparticle forming methods, to chemical mechanical polishing slurries, andto chemical mechanical polishing processes.

BACKGROUND OF THE INVENTION

Chemical mechanical polishing is one technique utilized to process theouter surface of various layers formed over a semiconductor wafer. Oneprincipal use of chemical mechanical polishing is to render an outerwafer surface of a layer or layers to be more planar than existed priorto starting the polishing. Only some or all of the outermost layer beingpolished might be removed during such a process.

In chemical mechanical polishing, both the wafer and the pad whichpolishes the wafer are typically caused to rotate, typically in oppositedirections during the polishing action. A liquid slurry is receivedintermediate the wafer and the polishing pad. The slurry comprises aliquid solution, typically basic, and a solid abrasive grit material,typically constituting particles of a consistent size (i.e., within 5nanometers of a typical selected size from around 25 to 100 nanometersin diameter). The action of the liquid solution and abrasive grit withinthe slurry intermediate the wafer pad and wafer imparts removal of outerwafer layers utilizing both chemical and mechanical actions.

One particular goal in the development of chemical mechanical polishingslurries is the provision of particles of substantially uniform size. Asidentified above, the typical individual particle size of chemicalmechanical polishing slurries is less than about 100 nanometers.Manufactured materials of this fine size are commonly referred to asnanomaterials or nanoparticles. Such materials find use in polishingprocesses and materials other than chemical mechanical polishing, forexample in batteries and in chemical reaction catalysts. Such materialshave historically been fabricated using combustion flame synthesismethods, such as for example described in U.S. Pat. No. 5,876,683 toGlumac et al. More recently, laser synthesis of nanoparticles is alsogaining interest, such as described in U.S. Pat. No. 5,695,617 toGraiver et al., Laser Synthesis of Nanometric Silica Powders, by M. Luceet al., and Synthesis of Polymerized Preceramic Nanoparticle Powders byLaser Irradiation of Metalorganic Precursors, by P. R. Strutt et al.,which are hereby incorporated by reference.

It would be desirable to improve upon the laser synthesis methods, andto produce improved chemical mechanical polishing slurries independentof the method fabrication.

SUMMARY

The invention comprises particle forming methods including laserpyrolysis particle forming methods, chemical mechanical polishingslurries, and chemical mechanical polishing processes. In but onepreferred implementation, a laser pyrolysis particle forming methodincludes feeding a first set of precursors to a first laser applicationzone. Laser energy is applied to the first set of precursors in thefirst laser application zone effective to react and form solid particlesfrom the first set of precursors. Application of any effective laserenergy to the solid particles is ceased and the solid particles and asecond set of precursors are fed to a second laser application zone.Laser energy is applied to the second set of precursors in the secondlaser application zone effective to react and form solid material aboutthe solid particles from the second set of precursors.

In one implementation, a particle forming method includes feeding afirst set of precursors to a first energy application zone. Energy isapplied to the first set of precursors in the first energy applicationzone effective to react and form solid particles from the first set ofprecursors. Application of any effective energy to the solid particlesis ceased and the solid particles and a second set of precursors are fedto a second energy application zone. Energy is applied to the second setof precursors in the second energy application zone effective to reactand form solid material about the solid particles from the second set ofprecursors. Preferably, at least one of the first and second appliedenergies comprises laser energy.

In one implementation, a chemical mechanical polishing slurry comprisesliquid and abrasive solid components. At least some of the abrasivesolid component comprises individually non-homogeneous abrasiveparticles.

In one implementation, a chemical mechanical polishing process includesrotating at least one of a semiconductor substrate and polishing padrelative to the other. A chemical mechanical polishing slurry isprovided intermediate the substrate and pad, and the substrate ispolished with the slurry and pad during the rotating. The chemicalmechanical polishing slurry comprises liquid and abrasive solidcomponents. At least some of the abrasive solid component comprisesindividually non-homogeneous abrasive particles.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a diagrammatic depiction of a laser pyrolysis particle formingmethod in accordance with an aspect of the invention.

FIG. 2 is a diagrammatic sectional view of a chemical mechanicalpolishing slurry abrasive particle.

FIG. 3 is a diagrammatic representation of an alternate laser pyrolysisparticle forming method in accordance with an aspect of the invention.

FIG. 4 is a diagrammatic view of an exemplary system used in a chemicalmechanical polishing process in accordance with an aspect of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

A laser pyrolysis particle forming method is indicated generally 14 withreference numeral 10. Such comprises a reaction flow path 12 having abeginning end 14 and a product collection end 16. Reaction flow path 12comprises at least first and second spaced laser application zones 18and 20, respectively. A pair of first precursor inlets 22 and 24 areprovided to reaction flow path 12 proximate beginning end 14 in advanceof first laser application zone 12. A pair of second precursor inlets 26and 28 are provided to reaction flow path 12 between first laserapplication zone 18 and second laser application zone 20. A pair ofinert gas inlets 30 and 32 are also provided intermediate first laserapplication zone 18 and second laser application zone 20. Such arepreferably provided for injection of purging gas at this point in theflow path, as will be described below. More or fewer precursor or inertinlets could of course be provided.

Reaction flow path end 16 includes a suitable trap 34 for collecting theformed particles. Unreacted precursor material, purge and/or carriergases are expelled via an exhaust 36.

At least one precursor is fed through one of first inlets 22 and 24 toreaction flow path 12 in advance of first laser application zone 18. Theprecursor or precursors are preferably provided as a gas. In aparticular example, where for example SiO₂ particles are to be formed,example reactive flow gases for lines 22 and 24 include a silane if suchas dichlorosilane, and O₂, respectively. An example flow rate range forthe dichlorosilane is from about 100 sccm to about 10 slm, with anexample flow rate for the O₂ also being from about 100 sccm to about 10slm. Temperature and pressure are preferably maintained within thereaction flow path outside of first and second spaced laser applicationzones 18 and 20 such that reaction of gases therein does not occur.

The one or more precursors fed from precursor inlets 22 and 24 are fedalong reaction flow path 12 to first laser application zone 18. Thedichlorosilane and oxygen in this example comprise a first set ofprecursors which is fed to first laser application zone 18. Laser energyis applied in first laser application zone 18 effective to react andform solid particles from the at least one precursor fed from at leastone of first inlets 22 and 24. An example preferred pressure is 200mTorr, with preferred temperature being ambient and not controlled. Theparticles formed are exemplified in FIG. 1 by the illustrated specks ordots materializing in laser application zone 18. An example laser is thecommercial PRC-Oerlikon 1500W fast-axial-flow CO₂ laser, such asdescribed in the Luce et al. article referred to in the Backgroundsection of this document. Other lasers, including excimer lasers, arealso of course utilizable, with KrF, ArF and Xe lasers being but onlythree additional examples. Any suitable power can be chosen effective toprovide suitable energy to cause a reaction and produce particles, andcould be optimized by the artisan depending upon gas flow rate, 11desired particle size, etc. The material of the particles formedutilizing the example dichlorosilane and O₂ feed gases willpredominately comprise SiO₂.

Such provides but one example process of first applying laser energy toa first set of precursors in a first laser application zone effective toreact and form solid particles from the first set of precursors.Alternate processing is of course contemplated. For example, and by wayof example only, precursors could be injected as liquid, and/or directlyinto the laser application zone as opposed to in advance thereof asdepicted and described relative to the most preferred embodiment.

The formed solid particles and any unreacted gas are fed from firstlaser application zone 18 along reaction flow path 12 to between thefirst and second spaced laser application zones 18 and 20, respectively.Such provides but one example of ceasing application of any reactioneffective laser energy to the solid particles after their initialformation in first laser application zone 18. At least one precursor isfed through at least one of second precursor inlets 26 and 28 intoreaction flow path 12 between first and second laser application zones18 and 20 having the solid particles flowing therein.

The precursor or precursors fed from at least one of second inlets 26and 28 and the solid particles are fed along reaction flow path 12 tosecond laser application zone 20. Such provides but one example offeeding the solid particles and a second set of precursors 11 to asecond laser application zone. Laser energy is applied in second laserapplication zone 20 effective to react and form solid material about thesolid particles from the at least one precursor fed from at least one ofsecond inlets 26 and 28. Such is shown in FIG. 1 by the enlarged orgrown particles appearing within second laser application zone 20.

The precursors provided from one or both of first inlets 22 and 24 canbe the same as that provided from one or both of second precursor inlets26 and 28, effectively forming substantially homogeneous solid particlesat the conclusion of applying laser energy in second laser applicationzone 20. In effect in this example embodiment, the first formedparticles in first laser application zone 18 are subsequently coated ina separate laser application zone 20 with the same material, effectivelylayering and growing particles which are substantially individuallyhomogeneous throughout. Application of at least two and perhaps morelaser pyrolysis steps for forming the particles might result in moreuniform size and shaped particles than might otherwise occur in a singlelaser application process.

Alternately by way of example, the first and second sets of precursorscan be provided to be different, with the second depicted laser energyapplication forming a solid material coating over the solid particleswhich is different from material of the solid particles formed in firstlaser application zone 18. Such might be utilized to provide optimizedsolid particles having different property outer and inner materials, forexample making the outer coating material or materials harder or softerthan the inner or initial material of the solid particles formed infirst laser application zone 18.

By way of example only, and continuing with the above example where SiO₂particles are formed in first laser application zone 18, thesubsequently formed solid material coating the particles as formed insecond laser application zone 20 might comprise an elemental metal, suchas elemental tungsten. For example, one or more precursors could be fedinto reaction flow path 12 from multiple inlets 26 and 28 to providesuitable reactive precursor materials, preferably in the form of gases,for feeding to second laser application zone 20. For example, a mixtureof WF₆ and an effective amount of H₂ could be fed as a mixture from eachof inlets 26 and 28, which would react in second laser application zone20 to coat the initially formed SiO₂ particles with elemental tungsten.

Where the first and second sets of precursors are different, it might bedesirable to provide an inert purge gas, such as N₂ or Ar, from inlets30 and 32 between first and second laser application zones 18 and 20 inadvance of precursor inlets 26 and 28. Such purging might be desired toeffectively dilute any unreacted remaining gases which have flowedthrough first laser application zone 18 to prevent reaction of the samein second laser application zone 20 where one or more discrete differentmaterial coatings are desired on the outside of the initially formedparticles. Such gases flowing from first laser application zone 18 andany purged gases injected by inlets 30 and 32 might be exhausted (notshown) from reaction flow path 12 in advance of subsequent precursorinjection at at least one of 26 and 28, or alternately flow in a dilutedmanner through second laser application zone 20.

The first and second sets of precursors might or might not share atleast one common precursor. The above described example is one where noprecursor material is common to the first and second sets. Consideralternately by way of example only a process wherein it is desired toform inner and outer layers of a particle which comprise differentnitrides. For example, consider forming the inner layer to comprise TiN,and forming the outer layer to comprise a harder WN material. NH₃ couldbe utilized as one of the precursor gases for supplying the nitrogencomponent of the formed nitrides in both the first and second sets ofprecursors. In one example, an abundance of NH₃ could be fed to reactionflow path 12 in advance of first laser application zone 18. An exampleadditional first precursor gas flowing from one or both of first inlets22 and 24 would be TiCl₄. The TiCl₄ and NH₃ would desirably react toform TiN particles in first laser application zone 18. Unreacted NH₃ andreaction byproducts would flow from first laser application zone 18, andcould be combined with WF₆ flowing out of one or both of second inlets26 and 28. The WF₆ and NH₃ would desirably react within second laserapplication zone 20 to form and outer coating of WN over the initiallyformed TiN particles. Additional NH₃ might be added to reaction flowpath 12 intermediate first laser application zone 18 and second laserapplication zone 20 through one or both of inlets 26 and 28.

More than two laser application zones or laser applications might alsobe utilized. Regardless, the processes most preferably are utilized 17to produce nanomaterials, whereby the ultimately formed solid particleshave a maximum diameter of no greater than 1 micron, and more preferableno greater than 100 nanometers.

FIG. 2 depicts an individually formed non-homogeneous particle 50. Suchcomprises an inner exemplary portion 52 formed within first laserapplication zone 18, and an outer coating 54 formed in second laserapplication zone 20.

The resultant formed particles are collected in trap 34 (FIG. 1), withremaining precursor inert or carrier gases being exhausted via line 36FIG. 1.

The above described processing depicted the first and second laserapplication zones as being different and spaced from one another along areaction flow path. Alternate considered processing in accordance withthe invention is shown in FIG. 3, whereby the first and second laserapplication zones comprise the same zones in different first and secondapplications of laser energy to the same or different precursors. Likenumerals from the first described embodiment are utilized whereappropriate, with differences being indicated with the suffix “a”, orwith different numerals.

Method 10 a in FIG. 3 differs from that depicted in FIG. 1 by provisionof a single laser application zone 18, and provision of a recycle stream60 from trap 34 back to immediately in advance of laser application zone18. In a preferred process in accordance with the FIG. 3 methodology,particles would initially be formed and collected in trap 34.Thereafter, the particles would be flowed back to reaction flow path 12a in advance of laser application zone 18, preferably in one or morediscrete single batches for uniformity in size control, and combinedwith the same or different precursors for subsequent coating thereof.Further alternately and less preferred, pulsed laser application mightoccur in a single or multiple laser application zone(s) relative to oneor more precursor gases to sequentially form multiple layered or coatedparticles.

Also contemplated in accordance with aspects of the invention isapplication of energy other than laser energy to effect some or all ofthe particle formation. For example, one or both of energy applicationzones 18 and 20 might comprise energy application sources other thanlaser. By way of example only, such might include a combustion flame, aplasma flame, photosynthesis such as UV light application, and otherheat energy such as passing the precursors/forming particles through apass-through furnace. Further, energy application zones 18 and 20 mightcomprise the same or different energy types.

The above described produced solid particles are preferably utilized informing a chemical mechanical polishing slurry at least a portion ofwhich contains such particles as the solid abrasive material within theslurry. Thereby, a preferred chemical mechanical polishing slurry inaccordance with the invention comprises liquid and abrasive solidcomponents. At least some of the abrasive solid components compriseindividually non-homogeneous abrasive particles produced by the abovedescribed or prior art or yet to be developed methods. Such particlesmight be characterized by two distinct material layers or more layers.Preferably, one of the two layers will envelop the other.

Slurries in accordance with the invention can be utilized in chemicalmechanical polishing processes in accordance with another aspect of theinvention, and as generally described with reference to FIG. 4. Anexemplary system shown in diagrammatic or schematic form for conductinga chemical mechanical polishing method in accordance with the inventionis indicated generally with reference numeral 60. Such comprises apolishing table or platen 62 having a polishing pad 64 receivedthereatop. A wafer carrier 66 is juxtaposed in opposing relationrelative to polishing pad 64. A workpiece 68, typically in the form of asemiconductor wafer, is received by wafer carrier 66. A slurry injectionport 70 is positioned to emit fluid onto pad 64 to be received betweenpad 64 and wafer 68 during polishing. Wafer carrier 66 and polishingtable 62 are typically mounted for independent controllable rotationrelative to one another. One or more wafer carrier head assemblies mightbe utilized for a single polishing table, and be mounted fortranslational movement as well relative to table 62. The above describesbut one very diagrammatic exemplary depiction of a chemical mechanicalpolishing system within which a method of the invention might beutilized.

In accordance with this aspect of a chemical mechanical polishingprocess in accordance with the invention, at least one of asemiconductor substrate and polishing pad are rotated relative to theother. A chemical mechanical polishing slurry is provided intermediatethe substrate and pad, and the substrate is polished with the slurry andpad during the rotating. The chemical mechanical polishing slurrycomprises liquid and abrasive solid components. At least some of theabrasive solid component comprises individually non-homogeneous abrasiveparticles, such as for example described above and producible inaccordance with the inventive and other processes.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A chemical mechanical polishing slurry comprising liquid and abrasivesolid components, at least some of the abrasive solid componentcomprising individually non-homogeneous abrasive particles characterizedby more than two distinct material layers, an outermost portion of themore than two distinct material layers comprising an elemental metal. 2.The chemical mechanical polishing slurry of claim 1 wherein thenon-homogeneous abrasive particles comprise an innermost portion, theinnermost and outermost portions comprising different materials.
 3. Thechemical mechanical polishing slurry of claim 2 wherein the material ofthe outermost portion is harder than the material of the innermostportion.
 4. The chemical mechanical polishing slurry of claim 2 whereinthe material of the outermost portion is softer than the material of theinnermost portion.
 5. The chemical mechanical polishing slurry of claim1 wherein the material of the outermost portion comprises W and thematerial of the innermost portion comprises SiO₂.
 6. The chemicalmechanical polishing slurry of claim 1 wherein the material of theoutermost portion comprises W and the material of the innermost portioncomprises TiN.
 7. The chemical mechanical polishing slurry of claim 1wherein the abrasive solid components have a maximum diameter of nogreater than 100 nanometers.
 8. The chemical mechanical polishing slurryof claim 1 wherein the abrasive solid components have a maximum diameterof no greater than 1 micron.